Republican U.S. presidential candidate Donald Trump said Sunday that “animals” standing with his rival Hillary Clinton and the Democrats were responsible for the firebombing of a North Carolina local Republican Party office.

The real estate mogul used the incident to further his claims that the presidential elections were “rigged” in Clinton’s favor. The GOP office in Hillsborough was torched and vandals also spray-painted “Nazi Republicans get out of town or else” with a swastika on a wall nearby overnight, local authorities said Sunday.

The flammable substance was ignited inside the building, burning some furniture and the inside of the building before causing damage to the building’s exterior. The substance encased in a bottle was thrown through one of the windows. Damage estimates are still unavailable but no one was injured in the attack.

“This highly disturbing act goes far beyond vandalizing property; it willfully threatens our community’s safety via fire, and its hateful message undermines decency, respect and integrity in civic participation,” Hillsborough Mayor Tom Stevens said in a statement. “I believe I speak for the overwhelming majority of people who make Hillsborough their home: Acts like this have no place in our community. Our law enforcement officials are responding quickly and thoroughly to investigate this reprehensible act and prosecute the perpetrators.”

Authorities are still investigating to determine who was behind this incident. But Trump on Twitter said, “Animals representing Hillary Clinton and Dems in North Carolina just firebombed our office in Orange County because we are winning.”

He offered no evidence for his claim. He later added, “ALL SAFE IN ORANGE COUNTY, NORTH CAROLINA. With you all the way, will never forget. Now we have to win. Proud of you all!”

Clinton also tweeted after the incident came to light calling the firebombing “unacceptable.”

“The attack on the Orange County HQ @NCGOP office is horrific and unacceptable. Very grateful that everyone is safe,” she said.

Trump has repeatedly tweeted to his 12.5 million followers about his theories of the election being “rigged.” Trump’s running mate Mike Pence said Sunday the Trump and Pence “will abide by the will of the American people.”

“We will absolutely accept the results of the election,” Pence reportedly said, adding that Trump’s claims of a “rigged” election stemmed from “the obvious bias in the national media.”

However, not long after Pence’s comments, Trump tweeted yet again saying, “The election is absolutely being rigged by the dishonest and distorted media pushing Crooked Hillary - but also at many polling places – SAD.”